The long term objective of this research is to improve the technology associated with the use of the white rot fungus, P. chrysosporium in the biodegradation of organopollutants. Under nutrient-limiting conditions, this fungus secretes a number of lignin and Mn-dependent peroxidases that account for its ability to degrade organopollutants. In vitro systems using purified enzyme, however, are unable to degrade the broad spectrum of compounds degraded by the fungus, especially with respect to extensively oxidized organopollutants. There is growing evidence that what is lacking in these in vitro systems are electron donors secreted by the fungus that propagate free radical mediated electron transfer reactions, that allow the fungus to initially reduce these oxidized molecules to better facilitate subsequent degradative reactions. The specific aims of this proposal are to identify these fungal electron donors, and establish whether or not they are involved in free radical mediated electron transfer reactions, initiated by lignin peroxidase, that are capable of reducing extensively oxidized organopollutants. The project relies heavily on analytical instrumentation, particularly ESR, NMR, and GC-MS spectrometers. A thorough study of this new concept in lignin peroxidase catalyzed degradative reactions promises to speed the application of P. chrysosporium to problems of environmental organopollutant cleanup.